Forget training for hours on end every week –– UK scientists have found just three 30-minute sessions is all you need for serious results.
Scientists from Liverpool John Moores University and the University of Birmingham have added to earlier research that found dedicating a third less time to the gym can be just as effective as long runs or bike rides.
They found doing just 90 minutes a week of high intensity interval training (HIT) and sprint interval training (SIT) was as effective as five hours of traditional endurance exercise for preventing heart disease, diabetes and other obesity-related chronic diseases.
"SIT involves four to six repeated 30 second 'all out' sprints on special laboratory bikes interspersed with 4.5 minutes of very low intensity cycling," explained lead researcher Dr Sam Shepherd.
"Due to the very high workload of the sprints, this method is more suitable for young and healthy individuals."
They recommend people who don't fit into that category do a HIT program.
"They involve 15-60 second bursts of high intensity cycling interspersed with 2-4 minute intervals of low intensity cycling," Dr Shepherd said.
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"HIT can be delivered on simple spinning bikes that are present in commercial gyms and are affordable for use at home or in the workplace."
The results from the tests showed a rapid reduction in health risks associated with obesity.
"It improved delivery of insulin and glucose to the skeletal muscle and improved burning of the fat stored in skeletal muscle fibres. Additionally, we found a reduced stiffness of large arteries which is important in reducing the risk of vascular disease," said co-researcher Matthew Cook.
Dr Lauren Banting, research officer at the Institute of Sport, Exercise and Active Living at Victoria University, told ninemsn interval training is ideal for people who are new to exercise.
"It's a great thing to do if you're not fit and you're wanting to see some improvements –– it's hard work but you see improvements quite quickly," she said.
"It also has that time-saving factor for busy people who don't have time to do an hour of exercise a day."
However Dr Banting said people can become bored with interval training, so once you've got your fitness levels up, it might be worth limiting it to one session a week and doing other activities that stimulate you.
"You have to concentrate quite a bit on the timer and after a period of time, that can get boring for some people who want to zone out when they exercise," she said.
To keep things interesting, she suggests mixing up your intervals and also focusing on your improving results.
"You can go from eight one-minute sprints to four four-minute blocks," she said.
"You'll keep getting faster and you really see the change."
If you prefer long-distance, continuous running, Dr Banting said you don't need to give it up in favour of intervals.
"There is a different kind of benefit you get –– instead of focusing on the timer, it is more relaxing," she said.
"The best kind of exercise is always the one that suits you best."
The research was published in The Journal of Physiology.